The main reason most people come to Ischia is for the thermal spas. The island sits on a volcanic field and hot springs emerge everywhere — not just in dedicated spa parks but rising through the sand at beaches like Maronti. Most spa parks charge entry; in return you get a series of pools at different temperatures, treatments, beach chairs, and usually a restaurant.
La Mortella (Via F. Calise 39, Forio) is the finest garden on the island and one of the best in Italy. Created by Susana Walton, wife of composer William Walton, in a former quarry at the base of Monte Zaro. Over 800 plant species, pools, cascades, a Greek amphitheatre for summer concerts, and a tea house. Open April–November, Tue/Thu/Sat/Sun 9am–7pm. Tel: +39 081 986220.
The Castello Aragonese at Ischia Ponte is the island's main historical monument — a fortress on a volcanic rock connected to the mainland by a causeway. The history stretches back to 474 BC. Inside: several churches, a convent, a nuns' cemetery, and a café. The views from the top are the best on the island.
At Sorgeto Bay, geothermal springs emerge directly on the sea floor, warming the water year-round. You can swim among the bubbles. The bay is accessible by boat from Ischia Porto or by steps from the road above.